Marrow nails are load-bearing devices which, using the so-called marrow-nailing technique, effect intramedullar stabilization of bone fractures by mechanical bridging.
Until recently, marrow nails were categorized into conventional marrow nails and locking nails. The considerations which led to this differentiation in this technical specialty, were based on the opinion that in spite of lacking a locking option, conventional marrow nails were the standard marrow nails to be used. This perception has become outdated, and a strong trend exists toward making locking nails the standard. However, within the category of locking nails there is also a trend toward marrow nails that are not hollow as well as marrow nails with various locking options.
The greatest degree of multiplicity is in marrow nails for the femur, with various kinds of locking. The reason for this can be found in the complexity of femur fractures and their treatment. Each type and location of fracture requires an appropriate type and location of locking at the proximal end of the nail.
The-various types and positions of proximal locking of femur marrow nails had led to a baffling multiplicity of structural varieties. This is extremely disadvantageous. For one thing, high inventory costs to hospitals are incurred, since all dimensions and types must be stored because the operation must take place immediately after admission of the patient. A multiplicity of various sets must also be prepared, which is another source of great expense. A special problem for small medical facilities, which deal with the majority of the world's patients, are the costs and the complexity of maintaining inventories and instrument sets. This often causes them to switch to other, less elegant methods of dealing with fractures.
A locking nail useful in a variety of situations is disclosed in DE-U1 9115200.3. It is equipped with an axially telescoping but torsionally strong casing, to permit compression and distraction of fragments of fractured hollow bones. The fastening of the telescoping casing relative to the marrow nail is achieved only by passing a bone screw through both parts, so that the position of the opening in the casing relative to the marrow nail's slot is not determined until the last step in the operation. Even after locking is complete, the screw can still be displaced along a relatively wide range of about 35% of the slot.